Documents of any kind are used to pay for goods. A rising number of goods, e.g. food, toys, medicine, tickets, and so forth are available at vending machines. The customer can pay at these vending machines or at automatic cash out devices with documents, e.g. bills, banknotes or coupons. The machines accepting the documents for a transaction have to provide a high reliability when validating the documents. There are several reasons why inserted documents are not acceptable. In case the documents are not acceptable, the machines should reject the documents back to the user to avoid financial loss for the company operating the machines. For example, the documents could be counterfeits and therefore not acceptable. Further, the documents could be damaged or torn. Customers using vending machines may try to fix damaged or torn documents. Often glue or tapes, in particular transparent tapes, may be used to fix the damaged or torn documents. These fixed documents might have less or no value for the company operating the machines. The tapes used for fixing the documents can be very thin (40-50 μm) and the tape pieces can be as small as 5 by 15 mm or even smaller. These factors may be considered when developing devices and systems for document accepting machines that are capable of detecting any kind of tapes, in particular transparent tapes, applied to a valuable document. A device for detecting such tapes on documents can avoid the acceptance of damaged or torn documents. Such devices can be included into document accepting machines. Therefore, these devices should have a compact design and a high reliability.